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Using LM35AH to verify thermostream accuracy within the range -40C to 125degC

Hi,

I was planning to use the LM35AH part to verify thermostream accuracy within the range -40C to 125degC, at least upto a level of +/-1degC. I have connected the VOUT pin to -Vs=-5V via a 100K resistor. The circuit schematic is given at the end. I had a few queries regarding this application, could you please provide help with these:

1.This part should be OK to measure the temperature of an impinging stream of air by directing the airstream from the thermostream temperature forcing equipment directly (and perpendicularly) on the case top right?

2.Is there any recommendation on the board size to be used(ie, is a larger board copper area recommended, or even a small PCB of say 3"x3" dimensions would be fine), and the number of layers. A normal two layer board would suffice?

3.A heat sink may not be required to be coupled with the part for this application right. Please note here the part body will be projecting up, and the only way the case would be in contact with the board ground layer will be through the ground terminal

4.I was also considering using the same board for checking the temperature forcing accuracy of a peltier contact based forcing system, wherein a metallic plunger would be in direct physical contact with the chip case, and heat transfer would be via direct contact. This part should be fine for this check too I hope?

Thanks,

Anoop

  • Hi Anoop,

    We will look into this and get back to you.

    -Michael Wong
  • Hi Michael,


    Ok

    Thanks,

    Anoop

  • Hi Anoop,

    Sorry for the late reply. See my answers below:

    1. That is correct. Note that the best way for temperature to reach the sensor itself is through the leads of the package.
    2. It is best to use a small board with as little thermal mass as possible. This is to decrease the thermal response time of the sensor.
    3. Heat sink is not required and the ground pin reaching the ground layer is okay.
    4. I'm not familiar with a peltier contact, can you provide more information? If you are talking about a metallic tip, such as a thermocouple, touching the case then that is okay.

    Your schematic looks fine by the way :)

    -Michael Wong
  • Hi Michael,

    Thanks a lot for the detailed replies. So I will use a smaller 2 layer board without any intermediate ground layers. Regarding peltier contact, I was talking about an equipment as seen in the image below, wherein there is a metallic plunger making contact with the top of the chip case

    http://www.ironwoodelectronics.com/products/sockets/socket_images/flex_tc.jpg

    Thanks,

    Anoop